1. Field of the Invention
The present invention generally relates to a refrigeration cycle apparatus, and, more particularly, to an improvement of a refrigerant separation system for varying the composition of a mixed refrigerant that circulates in a refrigeration cycle circuit in a refrigeration cycle apparatus in which a non-azeotropic mixed refrigerant consisting of plural types of refrigerants with different boiling points is filled.
2. Description of the Related Art
Recently, there is a demand for an air conditioner which uses heat attained by a heat pump type refrigeration cycle apparatus to ensure supply of hot water in addition to heating by a radiation panel that quickens the rising of heating as compared with the normal heating.
Conventionally, the above refrigeration cycle apparatus used in an air conditioner utilizes a single-component refrigerant, such as chloro-fluoro-carbon represented by R-22 having a relatively low boiling point, as being suitable for high efficiency operation. Since such a refrigeration cycle apparatus has a low condensing temperature, its performance is insufficient to satisfy the above demand. It is therefore desirable to develop a refrigeration cycle apparatus which is capable of functioning at high efficiency in a heating operation when a high temperature is required for supplying hot water, for example.
To fulfill this demand, recently a refrigeration cycle apparatus has been developed which has a mixed refrigerant consisting of plural types of refrigerants (normally, two types of refrigerants, namely, a high boiling point refrigerant and normal (low boiling point) refrigerant) filled in a refrigeration cycle circuit and can change the composition of the mixed refrigerant that circulates in this refrigeration cycle in accordance with the operational goal, as disclosed in Published Unexamined Japanese Applications No. 62-80452 and No. 59-197761. In other words, this refrigeration cycle apparatus can vary the composition (concentration) of a refrigerant which can increase the condensing temperature in a high temperature operation.
Varying the composition of a mixed refrigerant necessitates separation of a certain types of refrigerant from the mixed refrigerant as quick as possible, so that the concentration of a high boiling point refrigerant is high in the high temperature operation and, the concentration of a low boiling point refrigerant is high in the normal operation.
In the above-developed refrigeration cycle apparatus, a refrigerant separation system that is considered typical, is a separation method using distillation, which cools vapor of various types of refrigerants produced by heating a mixed refrigerant by means of a heating source to thereby restore it in liquid form for separation of a refrigerant.
The separation method using distillation requires a distiller taller than a certain height in order to provide high separation efficiency. Realizing this efficiency should inevitably result in enlargement of the refrigerant separation system and thus the overall refrigeration cycle apparatus. Further, this refrigeration cycle apparatus requires a heating source exclusively provided by disposing a heating pipe from the refrigeration cycle circuit or newly disposing a heater. In addition, this refrigeration cycle apparatus needs energy to be supplied to such a heating source and has no simple structure.
There is another known refrigerant separation system as disclosed in Published Unexamined Japanese Patent Application No. 62-162853, which separates a refrigerant by the thermal swing adsorption (TSA) method using an adsorbent material. In other words, the refrigeration cycle apparatus equipped with a refrigerant separation system employing the TSA method adsorbs a certain type of refrigerant in an adsorbent tank directly provided in a refrigeration cycle circuit and desorps the absorbed refrigerant by applying heat from a heater, to thereby vary the concentration of the refrigerant circulate in the refrigeration cycle circuit.
Based on this refrigerant separation system employing the TSA method, however, adsorption of a low boiling point refrigerant is done only by the adsorbent tank. This would require a significant amount of an adsorbent material filled in the adsorbent tank and enlarge the adsorbent tank and thus the overall refrigeration cycle apparatus, so that the refrigeration cycle apparatus is impractical for use in a home air conditioner or the like. Assuming that the pressure in the adsorbent tank of this refrigeration cycle apparatus is 6 Kg/cm.sup.2 (absolute pressure) and the refrigerant temperature is -5.degree. C., the amount of a filled adsorbent material necessary for changing the mixed refrigerant concentration ratio R-22/R-114=50 mol%/50 mol% (504 g/996 g) suitable for high temperature operation to a different concentration ratio R-22/R-114=80 mol%/20 mol% suitable for high efficiency operation by absorbing R-114, would be 967 g. Since the amount of the filled absorbent material is in proportional to the pressure in the adsorbent tank, it can be decreased by increasing the pressure in the adsorbent tank. The reduction in the amount of the filled adsorbent material is however restricted by the proper scale of the overall apparatus.